class_docstr: PTVVissimSimulation is responsible for the management of the vissim simulation.
docstr: Returns an available actor id. Otherwise, returns INVALID_ACTOR_ID.
docstr_tok: ["Returns","an","available","actor","id",".","Otherwise",",","returns","INVALID_ACTOR_ID","."]
code: def _get_next_actor_id(self):
      """
      Returns an available actor id. Otherwise, returns INVALID_ACTOR_ID.
      """
      all_ids = set(range(1, self._max_simulator_vehicles + 1))
      used_ids = set(self._simulator_vehicles.keys())
      available_ids = all_ids - used_ids
      if len(available_ids):
          return available_ids.pop()
      else:
          return constants.INVALID_ACTOR_ID
  
imports: import enum
  import logging
  import math
  import os
  import carla
  from ctypes import *
  from .None import constants
label_desc: Use image node_id 2 for calling the PTVVissimSimulation obj's underlying member method code with example usage: obj._get_next_actor_id() and returns: available_ids, constants